Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 2421-2440 of 5378
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Late Pleistocene-Holocene history of Svalbard ice caps and glaciers – integrating marine, terrestrial and lacustrine archives
(Doctoral thesis; Doktorgradsavhandling, 2021-03-25)The Arctic regions are affected by the modern climate change to a greater extent than the global average. This effect is called the Arctic amplification and is reflected in air temperatures rising with double rate and increased precipitation compared to the global average. The climate of Svalbard is strongly related to variations in the atmospheric and oceanic circulation patterns, and the archipelago ... -
On Automated Classification of Sea Ice Types in SAR Imagery
(Doctoral thesis; Doktorgradsavhandling, 2021-03-12)With the Arctic sea ice continuously decreasing in both extent and thickness, fast and robust production of reliable ice charts becomes more important to ensure the safety of Arctic operations. This thesis focuses on the development of automated algorithms for the mapping of sea ice from synthetic aperture radar (SAR) images. It presents a thorough background on the topics of sea ice observations ... -
Incident Angle Dependence of Sentinel-1 Texture Features for Sea Ice Classification
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)Robust and reliable classification of sea ice types in synthetic aperture radar (SAR) images is needed for various operational and environmental applications. Previous studies have investigated the class-dependent decrease in SAR backscatter intensity with incident angle (IA); others have shown the potential of textural information to improve automated image classification. In this work, we investigate ... -
Determination of the Dielectric Properties of Marine Surface Slicks Using Synthetic Aperture Radar
(Doctoral thesis; Doktorgradsavhandling, 2021-03-03)Over the course of the last three decades, Synthetic Aperture Radar (SAR) has proven itself to be an effective monitoring technology for marine applications. The clear benefits of using SAR as opposed to optical devices is that SAR is insensitive to cloud cover, lighting conditions and can also provide imagery to a high degree of resolution. Given these benefits, there is a large incentive to implement ... -
Wind at Northern Senja: Use of numerical weather prediction models for wind resource assessment
(Master thesis; Mastergradsoppgave, 2020-12-15)Wind resource assessment for establishing decentralized power production in remote and complex areas, is challenging due to a lack of observational data. To overcome this problem, Numerical Weather Prediction (NWP) models can be used to provide data where no observations exist. This thesis uses NWP models to do a wind resource assessment at northern Senja. The power grid in the area is prone to ... -
Veikimorener i Norrbotten, Nord-Sverige – dødislandskap og morenebelter fra siste istid. Geomorfologisk tilnærming og GPR-profilanalyse av veikimorener innen den nordligste buen av veikimorenebeltet – Lainiobuen
(Master thesis; Mastergradsoppgave, 2020-12-30)Skandinavias glasiasjonshistorie er enda ikke kontinuerlig sammensatt for weichselistiden. I forhold til det fennoskandiske isskjoldet har nye studier avdekket alternative geokronologiske tolkninger for tidlig og midt weichsel i Nord-Sverige. Veikimorenelandskapet ble dannet over en stadial-interstadial syklus korrelert til tidlig weichsel av Lagerbäck (1988). Dette motstrides av moderne vitenskapelige ... -
Structure and mechanism of a phage-encoded SAM lyase revises catalytic function of enzyme family
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-10)The first S-adenosyl methionine (SAM) degrading enzyme (SAMase) was discovered in bacteriophage T3, as a counter-defense against the bacterial restriction-modification system, and annotated as a SAM hydrolase forming 5’ methyl-thioadenosine (MTA) and L-homoserine. From environmental phages, we recently discovered three SAMases with barely detectable sequence similarity to T3 SAMase and without ... -
Biomarker and isotopic composition of seep carbonates record environmental conditions in two Arctic methane seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-12)Present-day activity of cold-seeps in the ocean is evident from direct observations of methane emanating from the seafloor, the presence of chemosynthetic organisms, or the quantification of gas concentrations in the water column and pore water solutes. Verifying past cold seep activity and biogeochemical characteristics is more challenging but may be reconstructed from proxy records of authigenic ... -
CO2 Increase Experiments Using the CESM: Relationship to Climate Sensitivity and Comparison of CESM1 to CESM2
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-14)We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that ... -
Vibrational spectroscopy beyond the harmonic approximation with the Polarizable Embedding model
(Doctoral thesis; Doktorgradsavhandling, 2021-02-23)In order to efficiently and accurately calculate vibrational properties for solvated systems, a theoretical framework for combining response theory with the Polarizable Embedding model (PE) has been derived and implemented, and is presented in this thesis. An open-ended recursive formalism is utilized through the implementation in OpenRSP, allowing energy-derivatives to be calculated analytically ... -
Environmental variability off NE Greenland (western Fram Strait) during the past 10,600 years
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)To reconstruct the climatic and paleoceanographic variability offshore Northeast Greenland during the last ~10 ka with multidecadal resolution, sediment core PS93/025 from the outermost North-East Greenland continental shelf (80.5°N) was studied by a variety of micropaleontological, sedimentological and isotopic methods. High foraminiferal fluxes, together with high proportions of ice-rafted debris ... -
Dinocyst stratigraphy of the Valanginian to Aptian succession (the Rurikfjellet and Helvetiafjellet formations) from Spitsbergen, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-11)In order to improve the understanding of how the high northern latitudes responded to the escalating warming which led to the middle Cretaceous super greenhouse climate, more temperature proxy records from the High Arctic are needed. One of the current obstacles in obtaining such records is poor age control on the Lower Cretaceous strata in the Boreal region. Here, we provide a biostratigraphic ... -
Passive seismic recording of cryoseisms in Adventdalen, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-20)A series of transient seismic events were discovered in passive seismic recordings from 2-D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images using an apparent offset re-sorting and inter-trace delay minimisation technique to locate the seismic source, followed by ... -
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard
(Journal article; Tidsskriftartikkel, 2020-11-10)The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with active gas venting and were the focus of drilling and coring with the seafloor‐deployed MARUM‐MeBo70 ... -
Evolution of a shear zone before, during and after melting
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-03)Partial melt in the deforming mid- or lower continental crust causes a strength decrease and drives formation of lithological heterogeneities. However, mechanisms of formation of syn-melt deformation zones and strain partitioning in partially molten rock remain poorly understood. We use field and microstructural observations to unravel the evolution of a partial melt shear zone, Seiland Igneous ... -
Klimanøytral miljøpark – en vurdering av kostnader og nytteverdi for klimagassreduserende tiltak
(Master thesis; Mastergradsoppgave, 2020-12-14)Remiks AS har gjennom flere år gjort en kartlegging av klimagassutslipp knyttet til egen virksomhet. På bakgrunn av dette er det iverksatt flere tiltak på aktuelle områder som har blitt identifisert. Det er i midlertidig ikke sikkert at investeringene som er gjort er de mest effektive tiltakene om man vurderer kostnadene mot klimanytten. Denne studien vil vurdere tiltakene solenergi, biodrivstoff, ... -
Wideband Self-Interference Cancellation Using Multi-Tap Filter in Radar Front End
(Mastergradsoppgave; Master thesis, 2020-12-14)The largest hurdle in full duplex wireless systems is the self-interference introduced by the transmitted signal into the received signal. In multi antenna systems this interference is caused by the direct coupling between the transmitting and receiving antennas. In systems where the transmitter and receiver uses the same antenna the interference is caused by inadequate isolation between the ... -
Performance and Future Potential of Solar Photovoltaics in Arctic Settlements
(Master thesis; Mastergradsoppgave, 2020-12-15)Data from a solar photovoltaic (PV) installation on Svalbard Airport Longyear has been analyzed to investigate performance of solar photovoltaics in the Arctic. Results show that the average capacity factor at the facility is 5.6 % after its first two full years of production. While the production in the winter is zero, monthly capacity factors are observed to be as high as 16 % in the summer. On ... -
Towards detection and classification of microscopic foraminifera using transfer learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-06)<p>Foraminifera are single-celled marine organisms, which may have a planktic or benthic lifestyle. During their life cycle they construct shells consisting of one or more chambers, and these shells remain as fossils in marine sediments. Classifying and counting these fossils have become an important tool in e.g. oceanography and climatology. <p>Currently the process of identifying and counting ... -
The Raunis section, central Latvia, revisited: first luminescence results and re-evaluation of a key Baltic States stratigraphic site
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-08)In interstadial deposits, sand interbeds gain limited consideration in comparison with organic sediments, and therefore tend to be underrepresented in paleoenvironmental reconstructions. The Raunis site, central-eastern Latvia, is an example where organic beds have already gained some attention and been used to understand the complex interactions between advance and retreat of the Scandinavian Ice ...